Connectors with switchable terminal loads

ABSTRACT

Switchable grounded terminal loads are built into, or otherwise coupled to, connectors on motherboards and control devices. The terminal loads are coupled to the bus termination at the connector when the connector is “stuffed” (connected to a mating connector). The switchable grounded terminal loads replace dummy connectors in preventing empty “unstuffed” connectors from increasing error risks on active channels.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional application of, and claims the benefitof priority from, U.S. Non-Prov. patent application Ser. No. 14/757,951filed Dec. 26, 2015, which is entirely incorporated by reference herein.

FIELD

Related fields include electrical connectors, and more particularlytechniques for controlling impedance in empty slots, tabs, plugs, orsockets connected to central processing units (CPUs) or other processorsor controllers.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of stuffed (connected) and unstuffed (empty)fixed connectors on a motherboard.

FIG. 2 is a state diagram for a connector with a switchable terminatedload.

FIGS. 3A-3C illustrate a terminal load engaged and disengaged by springforces in a compression clip.

FIGS. 4A-4B are views of a mechanical switch.

FIG. 5 is a connector with switchable grounded terminal loads on tworeceptacle walls.

FIG. 6 is an adaptation of the two-switch, two-load schema for malefixed connectors.

FIG. 7 is a connector with a single switchable terminal load.

DETAILED DESCRIPTION

For purposes herein, the following terms shall be associated with thefollowing definitions:

Detachable Connector: A connector that can engage to, and disengagefrom, a Fixed Connector; for example, a tab on a memory card that mateswith a slot on a motherboard or a plug at the end of a cable that mateswith a socket in a device housing.

Fixed Connector: A connector permanently attached, directly or through acable, to a controlling component such as a motherboard or a controllingdevice such as a desktop computer or mobile phone which may or may notbe accessible through a device housing.

Computers and electronic devices are made with various fixed connectorsboth inside and outside the housing. Connectors accessible only frominside the housing provide flexibility for manufacturing, upgrading, andrepair. For example, a motherboard may have several expansion slots formemory cards, audio/video cards, networking cards, and the like. Thesame motherboard may be installed with most of the expansion slots emptyin a basic model, or with most of the expansion slots full in ahigher-end model. An end user who initially buys a basic model can fillup more of the expansion slots later to improve or expand functionality.If either a card or a slot is damaged, the bad card may be swapped for agood card or the good card may be moved from the bad slot to an emptygood slot. Storage devices that can be easily attached to and detachedfrom motherboards provide similar configuration flexibility.

Connectors accessible from outside the housing enable connection of thedevice to peripheral devices, peer devices, and networks. Portabledevices in particular may be connected to, and disconnected from,multiple power sources, display devices, scanners, printers, keyboards,mice, and docking stations several times a day.

In many devices, some of the fixed connectors are likely to bedisconnected (empty, or “unstuffed”) at any given time. Some systems maytolerate emptiness of some types of fixed connectors, but others mayincrease noise, degrade signal quality, or cause other problems thatwould be absent if the connector were connected (occupied, or“stuffed”). Accordingly, passive “dummy” cards or plugs are made for avariety of connector types. They do not add any new functionality to thedevice, but they provide a terminal load, sometimes with grounding, sothat the fixed connector performs as if it were engaged with adetachable connector rather than being empty. Although they remedy someof the problems, dummy cards may add significant cost to the system.

To avoid exposing unconnected pins and plugs to external environments orforeign objects, many fixed connectors may be female, with recessedelectrical contacts. However, embodiments of the disclosed concepts maybe adapted for fixed male connectors as well as fixed female connectors.

FIG. 1 is a block diagram of stuffed (connected) and unstuffed (empty)fixed connectors on a motherboard. The baseboard routing 101 is shownconnecting the CPU 105 to each of a pair of T-topology buses 109.1 ad109.2.

The branches of T-topology bus 109.1 terminate in one of the simplestfixed connector types. The fixed connector 102 is “stuffed,” i.e., amating detachable connector 103.1 having one or more pins or contacts isengaged with fixed connector 102. The fixed connector 104 is“unstuffed,” i.e., empty or unconnected. The absence of a contact leavestermination 107 “floating,” i.e., unloaded and ungrounded.

Floating termination 107 may introduce an impedance mismatch thatdegrades the performance of T-topology bus 109.1 and increases the riskof error for the component connected to CPU 105 by detachable connector103.1 and stuffed fixed connector 102. For example, some dual in-linememory modules (DIMMs) may have a “Low” (0-1%) risk of write errors anda “Medium” (1-10%) risk of read errors on a T-topology bus 109.1 if bothfixed connectors are stuffed, but if one fixed connector is unstuffedthe risk of both read and write errors may increase to “High” (10-50%).Changing the design of T-topology bus 109.1 for better performance withone stuffed fixed connector 102 and one unstuffed fixed connector 104may unsatisfactorily compromise the bus performance with two stuffedfixed connectors while never quite reaching the desired performancelevel with one stuffed and one unstuffed.

At the terminations of T-topology bus 109.2, stuffed fixed connector 112and unstuffed fixed connector 114 eliminate floating terminations.Grounded terminal loads 119.1 and 119.2 are switchably coupled to theterminations of T-topology bus 109.2. The switch 117.1 is open when thefixed connector 112 is stuffed with detachable connector 103.2,disconnecting grounded terminal load 119.1 from its branch of T-topologybus 109.2 so that the only connection of stuffed fixed connector 112 iswith detachable connector 103.2. Stuffed fixed connector 112 may thusbehave like conventional stuffed fixed connector 102. The unstuffedfixed connector 114 has switch 117.2 that is closed so that itstermination of T-topology bus 109.2 is connected to grounded terminalload 119.2 instead of floating. The grounded terminal load 119.2 may bedesigned to match the impedance of detachable connector 103.2 so thatT-topology bus 109.2 may behave as if both fixed connectors are stuffedeven if one or both fixed connectors are in fact unstuffed.

The grounded terminal loads 119.1, 119.2 are illustrated as schematicresistors, but in some embodiments they may include other types ofimpedance-matching components, depending on the characteristics ofdetachable connector 103.2. The grounded terminal loads 119.1, 119.2and/or switches 117.1, 117.2 may be positioned in, on, or around fixedconnectors 112, 114 in any suitable location and orientation.Additionally, in some embodiments, switches 117.1, 117.2 may be actuatedby any convenient effect that may be made to coincide with engagementand disengagement of the detachable connector 103.2 from the fixedconnector 112. In some embodiments, switches 117.1, 117.2 actuatemechanically, such as by a spring which has the advantage of notrequiring any added electrical power to operate the switch.

For example, detachable connector 103.2 may be the connector tab on amemory card, e.g., a DIMM card. In some embodiments, detachableconnector 103.2 may be a connector tab for an audio-visual (A/V) card,an option card, a graphics card, a Peripheral Component InterconnectExpress (PCIe) card, a PCIe card raiser. In other embodiments,detachable connector 103.2 may be a Serial AT Attachment (SATA)detachable connector. In yet other embodiments, detachable connector103.2 may be a Universal Serial Bus (USB) plug or a DisplayPort (DP)plug.

FIG. 2 is a state diagram for a connector with a switchable terminatedload. In state 202 (e.g., when initially installed), the groundedterminal load is engaged by default and the fixed connector isterminated and grounded. State 202 may be a default state whenever thesystem power is on and the fixed connector is unstuffed. In someembodiments, state 202 may persist when the power is off and the fixedconnector is unstuffed, to make it the default power-up state.

Stimulus 203, in which the detachable connector is engaged (optionallyfollowed by stimulus 205, in which an actuator opens the switch),triggers a state change to state 206, in which the fixed connector isdisconnected from the grounded terminal load. From there, stimulus 207,in which the detachable connector is disengaged (optionally followed bystimulus 209, in which the actuator closes the switch, triggers a statechange back to state 202). The actuator inputs are optional because someembodiments change states without requiring an “actuator” per se as aseparate part. In such embodiments, the switching is actuated by amechanical reaction of existing parts to the insertion or removal of thedetachable connector.

FIGS. 3A-3C illustrate a terminal load engaged and disengaged by springforces in a compression clip. FIG. 3A is a perspective view of stuffedand unstuffed fixed connectors with cutaways to show interiorcompression clips. These connectors are generic and not intended torepresent any particular manufacturer's product. Fixed connectors 312and 314 are mounted on baseboard 301, which may be, for example, aprinted circuit board (PCB). They may be enclosed in casings 342 and 344with (or, alternatively, without) end latches 332.1, 332.2, 334.1, and334.2.

Inside the casings 342, 344 (which are shown partially cut away to showthe interior structure), the fixed connectors 312 and 314 may includespring-loaded clips with compression jaws 322.2, 324.2. The detachableconnector 303 may be a tab extending from another PCB or a packagedmodule. Clip jaws 322.1, 322.2 of stuffed fixed connector 312 expand toadmit detachable connector 303 and exert a compressive restoring forceto hold detachable connector 303 securely in place. Latches 332.1 and332.2 are shown in a horizontal locked position, which also acts to holdthe detachable connector in place.

In some embodiments, fixed connectors 312 and 314 may include conductivepins or leads such as fixed connector contacts 352, 354. In stuffedfixed connector 312, fixed connector contacts 352 make electricalcontact as well as mechanical contact with detachable connector contacts313 (e.g., pins or “goldfingers”) of detachable connector 303. Forsimplicity, very short connectors with only a few pins are illustrated,but those skilled in the art understand that the same type of connectormay be made in a variety of lengths with varying numbers of pin, strip,or similar connections.

In unstuffed fixed connector 314, the absence of a detachable connectorallows clip jaw 324.2 to relax to an equilibrium position angled furthertoward a longitudinal midplane than the position of clip jaw 322.2. Thelatches 334.1 and 334.2 are shown tilted outward from the ends, whichposition allows the detachable connector to be inserted or released.

FIG. 3B is a sectional view of stuffed fixed connector 312 throughsection A-A of FIG. 3A, omitting the casing. In some embodiments, fixedconnector contacts 352 may be connected to vias 311 that extend throughone or more layers of baseboard 301. The grounded terminal load forstuffed fixed connector 312 may include terminal contact 309, impedanceelement 319, and ground connection 329. In some embodiments, groundconnection 329 may connect to a ground plane of baseboard 301.

When detachable connector 303 is inserted in the clip, it exertsexpansion force 310 on clip jaws 322.1 and 322.2. Clip jaws 322.1 and322.2 “push back” with a restoring force to hold detachable connector303 in place, but are held too far apart by detachable connector 303 totouch terminal contacts 309. Therefore, when fixed connector 312 isstuffed, the fixed connector contacts 352 connect only with thedetachable connector contacts 313, and the grounded terminal load isunconnected to the fixed connector contacts 352.

FIG. 3C is a sectional view of unstuffed fixed connector 314 throughsection A-A of FIG. 3A. When detachable connector 303 is absent from theclip, it exerts no expansion force on clip jaws 324.1, 324.2. Withoutthat opposing force, restoring force 320 pushes clip jaws 324.1, 324.2inward toward their equilibrium position. Somewhere along the path ofrelaxation of clip jaws 324.1, 324.2, the fixed connector contacts 354touch terminal contacts 309. Therefore, whenever fixed connector 314 isunstuffed, the restoring force of clip jaws 324.1, 324.2 automaticallyconnects the grounded terminal load 309, 319, 329, terminating the fixedconnector contacts 352 so that unstuffed fixed connector 314 does nothave a floating termination.

FIGS. 4A-4B are views of a mechanical switch. The switches shown in thefigures may be made small enough to build into some types of connectors.FIG. 4A shows two different magnifications of part of an unstuffed fixedconnector with the switch closed to connect the terminal load. Unstuffedfixed connector 414 includes a cavity 444. Cavity 444 holds two arms,stationary arm 424 and moveable arm 434, that constitute the switch. Themoveable arm 434 has a first conductive contact 433, which in unstuffedfixed connector 414 touches a second conductive contact 423 onstationary arm 424. When the first conductive contact 4343 and thesecond conductive contact 4243 are touching, current can flow betweenstationary arm 424 and moveable arm 434. One of stationary arm 424 ormoveable arm 434 may be connected to a grounded terminal load (notshown). Moveable arm 434 also features a bend 435 that protrudes throughan opening into receptacle 454 of unstuffed fixed connector 414, wherethe detachable connector is normally inserted with a running-and-slidingfit or an interference fit, depending on the type of connector.

FIG. 4B shows two different magnifications of part of a stuffed fixedconnector with the switch open to disconnect the terminal load.Detachable connector 403 is inserted in the receptacle of fixedconnector 412 using downward pressure 410. When detachable connector 403encounters bend 435 of moveable arm 434, it pushes bend 435 out of thereceptacle and back into the cavity in direction 420. Meanwhile, secondcontact 423 is held in place by locating feature 422 in the cavity wallof the connector body. The rigidity of moveable arm 434, including bend435, moves the first contact 433 off of and away from second contact 423in direction 430, thereby opening the switch and disconnecting thegrounded terminal load (not shown in this view).

Materials for the first contact and second contact may be any conductivematerial that can withstand the expected number of couplings anduncouplings over the life of the connector. Gold or silver may be chosenfor connectors that are connected and disconnected less often. Copper,aluminum, or harder alloys containing gold or silver may be preferredwhere connecting and disconnecting will be done more often. The bend andcontact-end section of the moveable arm may preferably be a rigidmaterial for repeatable motion while the section of the moveable armbelow the bend may either provide an elastic restoring force itself(e.g., work-hardened metal) or be rigid and coupled to a spring thatprovides the restoring force.

FIG. 5 is a connector with switchable grounded terminal loads on tworeceptacle walls.

The connector 512 has switches on opposing sides of receptacle 554.Alternatively, switches may be on adjacent walls; preference may dependon the location of the bus terminations that benefit from terminationloads. Unstuffed connector 512 has a pair of mirror-image cavities 544.1and 544.2. Each one has a stationary arm 524.1 or 524.2 connected to aterminal load that includes an impedance element 519.1 or 519.2 and aground connection 529.1 or 529.2. The grounded terminal loads519.1+529.1, 519.2+529.2 may be coupled to either the stationary arms524.1, 524.2 or the movable arms 534.1, 534.2. However, in someembodiments, it may be preferable to use the stationary arm 524.1, 524.2to avoid transferring repeated stresses to the grounded terminal loads519.1+529.1, 519.2+529.2.

While receptacle 554 is empty, first contacts 533.1 and 533.2 on movablearms 534.1, 534.2 will touch second contacts 523.1 and 523.2 onstationary arms 524.1 or 524.2 to provide electrical couplings to thegrounded terminal loads 519.1+529.1, 519.2+529.2. If detachableconnector 503 is inserted in receptacle 554, it will displace two bends535.1 and 535.2 of moveable arms 534.1 and 534.2. When bends 535.1 and535.2 are pushed back into cavities 544.1, 544.2, first contacts 533.1and 533.2 on movable arms 534.1, 534.2 will move away from secondcontacts 523.1 and 523.2 on stationary arms 524.1 or 524.2 to eliminateelectrical couplings to the grounded terminal loads 519.1+529.1,519.2+529.2.

FIG. 6 is an adaptation of the two-switch, two-load schema for malefixed connectors. At this writing, a majority of fixed connectors arefemale because the recessed contacts on a female connector are lessexposed, and thereby may be less vulnerable to accidental shorting andother problems. However, the disclosed approach may also work with malefixed connectors.

Connector 614 is a male connector compatible with mating connector 613.Instead of an inner receptacle, the space to be occupied by the matingconnector 613 is an outer perimeter 664. The configuration may be verymuch like FIG. 5—dual mirror-image cavities 644, stationary arms 624,first contacts 623, moveable arms 634, second contacts 633, impedanceelements 619, and ground connections 629—except that the bends andopenings face outward rather than inward. Bends may be replaced withsolid (e.g., molded) tabs 645 in any of the designs.

FIG. 7 is a connector with a single switchable terminal load. Thisapproach may be especially suitable for slots that mate with tabs 703with contacts 713 on the side, so that the bottom surface may be used toswitch the terminal load, which may include impedance element 719 andground connection 729. This terminal load is coupled to stationary arm724 at a right angle. As with the other illustrated examples, bend 735,of length 764, in moveable arm 734 protrudes into receptacle 754, in thespace for the currently absent mating connector 703, and first contact733 touches second contact 723 to close the switch and couple the bustermination(s) to the terminal load. When inserted, mating connector 703will push bend 735 down to move first contact 733 away from secondcontact 723 to decouple the connector from the grounded terminal load.

Non-limiting examples of the types of connectors that could potentiallybe customized with switchable terminal loads include PeripheralComponent Interconnect Express (PCIe), USB, DisplayPort, SATA, raiser,option cards, and AN boards. Models predicted that connectors withswitchable terminal loads yield about the same error rate as connectorswith more expensive dummy mating connectors installed.

The preceding Description and accompanying Drawings describe examples ofembodiments in some detail to aid understanding. However, the scope ofprotection may also include equivalents, permutations, and combinationsthat are not explicitly described herein. Only the claims appended here(along with those of parent, child, or divisional patents, if any)define the limits of the protected intellectual-property rights.

We claim:
 1. An apparatus, comprising: a casing having an opening; astationary arm inside the casing; a moveable arm inside the casingexcept for a portion protruding through the opening into a space of thecasing to be occupied by a mating connector, the moveable arm not in asame plane as the stationary arm; and a terminal load coupled to thestationary arm and a bus termination coupled to the moveable arm;wherein a first contact on the moveable arm and a second contact on thestationary arm touch each other when the mating connector is absent fromthe space of the casing to be occupied by the mating connector, therebycoupling the bus termination with the terminal load; and whereinengaging the portion of the moveable arm with the mating connectorcauses the first contact to rotate away from the second contact, therebyuncoupling the bus termination from the terminal load.
 2. The apparatusof claim 1, wherein the second contact and an adjacent end of thestationary arm are held in place by a slot in a wall of the casing. 3.The apparatus of claim 1, wherein the space of the casing to be occupiedby the mating connector comprises a receptacle.
 4. The apparatus ofclaim 1, wherein the space to be occupied by the mating connectorcomprises a perimeter.
 5. The apparatus of claim 1, wherein the openingis located in a bottom wall of a receptacle.
 6. The apparatus of claim1, wherein the portion of the moveable arm protruding through theopening comprises a bend.
 7. The apparatus of claim 1, wherein adirection of motion of the mating connector into the space of the casingto be occupied by the mating connector is parallel to the stationaryarm.
 8. The apparatus of claim 1, wherein a direction of motion of themating connector into the space of the casing to be occupied by themating connector is perpendicular to the stationary arm.